Transformer winding



March 8, 1932. H. 1 COLE TRANSFORMER WINDING Filed June 8', 1928 ATTORNEY Patented Mar. 8, 1932y UNITED STATES PATENT OFFICE HORACE L. COLE, OF SHARON, PENNSYLVANIA, ASSIGNOR- T WESTINGHOUSE ELC- TRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA TRANSFORMER WINDING Application led June 8, 1928. Serial No. 283,890,

My invention relates to electrical transformers and particularly to the arrangement and connections of the windings of transformers.

` ing to deliver both low current and low voltage and of sufficient react-ance to insure safe operation upon the occurrence of a short l circuit of the winding.

lIn auto transformers, and, especially,

when'tap-changing devices are employed to vary the effective number of turns near the end of the transformer winding, and, upon the occurrence of surges in the power supply circuit, heavy surges may be caused to flow directly from the line into the transformer through the end turns of the windhere is danger of excessive voltage reaching the tap changer and terminal connections when there are relatively few end turns between the line and the tap changer. Vih'enY used in windings that .require tap changers or other devices to be placed near the line leads, my invention interposes additional surge impedancebetween the line and the part to be protected, without materially affecting the normal operating characteristics of the transformer. Je

An object of my invention, generally stated, is to provide means for limiting the -iow of current in transformer windings during abnormal operating condi-tions.

A further object of my invention isto provide a'transformer winding of high internal reactance and capable of delivering av low voltage and low current.

Another object of my inventionis to provide surge or short-circuitl protection to a transformer winding. l Other objects of my invention will become apparent to those skilled in the art when ings, in which,

the following description is considered in conyunction with the accompanying draw- Fig'ure l of the drawings is a diagrammatic view of a transformer having a tertiary winding connectedin accordance with my invention;

Fig. 2 is a diagrammatic view of the windngs and connections of the transformer shown in Fig. 1;

Fig. 3 is a diagrammatic view of an vauto transformerv in which a number of turns are reiersed in Iaccordance with my invention; an

Fig. 4 is a diagrammatic view of the windings and connections of the auto transformer shown in Fig. 3.

In the transformer shown in Fig. 1, a primary or high-voltage winding 10 is wound upon a core 11 and may have its terminals connected to a suitable source of alternatingcurrent power. The secondary winding 12 consists of a less number of turns than the primary winding 10 and may, therefore, be considered as a low-voltage winding. The secondary winding 12 is so disposed upon theV core 1l that energy delivered to the primary winding 10 from its source of supply is transferred to thesecondary winding 12, in a manner well known in the art, to energize a supply line at a lower voltage than that to which the primary winding 10 is connected.

'An auxiliary or tertiary `winding 13 is woundupon the core 11 and is disposed to supply a relatively low current at low voltage, for the operation of meters and other devices requiring relatively low kva. to operate, the power delivered by the tertiary winding 13 being proportional to that of the main windings. The tertiary Winding 13 is composed of Vtwo coils 14 and 15, which are connected together in series relation, but are so Woundupon the core 11 that the voltage induced in the coil 14 is always opposite to that induced in the coil 15. The terminal voltage of the tertiary winding 13 is, therefore, the difference between the voltage induced in the coil 14 and the voltage induced in the coil 15, and the winding 13 thereby provides a voltage of low value from a windin of a relatively great number of turns which is adequately protected against short circuits and of suiicient reactance to permit its safe and etlicient operation.

From an inspection of Fig. 2, the relation betweenthe magnitudes of the voltages induced in the windings 10, 12 and 13 will be readily apparent. The winding 1() supplies energy to both the windings12 and 13, and the ratio of transformation between the various windings is proportional to the turns of the corresponding windings, as is well known in the art. Furthermore, it will be apparent that, with the coils 14 and 15 connected in the relation shown, and with the coil 14 comprising a few more turns than the coil 15, as shown, the voltages induced therein will be in opposite directions so that the resultant voltage will be a voltage equivalent to only a few turns of the winding 14. The provision of the coil 15, therefore, causes additional reactance in the tertiary winding 13 and enables the tertiary winding to produce a low voltage and a low curren v When such tertiary winding is' used for metering purposes, as is often desired, the

disposition of-the winding on the core withv respect to the main windings may be so made that, when the main windings are loaded and delivering power, the tertiary voltage will be proportional to the voltage of one or the other windings. In this way, the tertiary may be used for measuring the poweron the primary side or on the secondary side, if so designed, giving a safe and reliable source of potential without the use of a special potential transformer. v

The auto transformer shown in Figs. 3 and 4 comprises a core. 16, which may be ofthe shell type, about which a plurality of coils are wound. The source of primary voltage is connected between the conductors 17 and 18 and energizes the complete winding comprising the several windings or sections 19, 20, 21 and 22, all of which are connected in series-circuit relation.

The secondary or low voltage of the auto transformer is taken from the conductors 17 and 23 and may be varied by connecting any of the taps 24 with any of the taps 25, thereby disconnecting and bypassing a portion of section 20, or section 21, of the transformer winding, or a portion of each, and, in this way, reducing the number of effective turns connected between the primary leads 17 and 18. While, in the figure and throu hout the description, the windings connecte between the conductors 17 and 18 have been designated as the primary land 'those between 17 and 23, the secondary, the auto transformer may be operated with the windings between 17 and 18 as the secondary and those between 17 and 23 as the primary, with the same effect, so far as the invention is concerned. The operation of tap-changin devices is well known inthe art, and, there ore, it is deemed unnecessary to embody a full description of their operation herein.

As will be seen from the diagrams, the com bination of the sections 19, 20 and 21 of the winding will constitute the main or effective portion of the transformer winding, that is, the portion which will govern the direction of the voltage between the leads 17 and 23. The auxiliary winding 22 is of opposite polarity to the sections 19, 20 and 21 and is connected in series with the sections 19, 20 and 21 adjacent to the section 21, between the section 21 of the transformer winding and line conductor 18.

By the connection of a section of winding, such as 22, having a polarity opposite to that of the main transformer winding in series` circuit relation with an auto transformer, it is possible to rotect the end turns of the transformer winding from any surges which may occur in the supply line.

From the diagram of Fig. 4, it will be apparent that, with the voltage difference represented by the distance between the conductors 23 and 18, it will be difficult to provide-a tap-changing device to satisfactorily control the magnitude of this variable voltage without placing the tap-changing connections so close to the end turns of the winding and thus so reducing the reactance between the conductors 23 and 18 that operation of the device would be unsafe upon the occurence of a power surge or other abnormal condition. The application ofthe section of winding 22, therefore, facilitates variation in the voltage delivered to the conductors 17 and 23, as well as affords protection from line surges to the ta -changing mechanism and to those turns o the coils 20- and 21 which have been bypassed through the operation of a tap-changer mechanism.

Since it will be ossible to modify the embodiments set fort and adapt them to numerous applications without departing from the spirit and sco e of my invention, 1t is intended that the oregoing description shall be construed as merely illustrative and not in a'limiting sense. I

' I claim as my invention:

1. In a transformer,avariablewindingprovided with lvoltage-changing taps, said staps being 'disposed to control the end turns of the effective winding, an auxiliary winding section of opposite polarity to the variable windralty of turns connected in series-circuit relation, two adjacent winding sections being provided with taps for varying the points of connection therebetween, one of sald winding sections being connected between said tapped sections and the terminal of the transformer having turns oppositely disposed with respect to the turns of the other winding sections, whereby the terminal voltage of said winding is the difference in the voltages in.

duced in the oppositel disposed turns.

In testimony whereo ,I have hereunto subscribed my name this 29th day of Ma 1928.

HORACE L. C LE. 

